text:
Does all of the air that 'leaks' from the bottom of the wingtip to the top create a vortex?
What I'm asking is does all of the air that spills from the high pressure bottom of the wingtip get pulled by the low pressure top of the wing? So some of the air curls around the wingtip to make a vortex, but does that mean all of the air gets pulled by the top of the wing and make a vortex? Does some air escape past the low pressure top of the wing and not make a vortex at all?
Thanks!

To address this question, let's review the aerodynamics involved in aircraft wingtips and the formation of wingtip vortices.
Lift generation
A wing generates lift by creating a pressure difference between its upper and lower surfaces. The air pressure is higher under the wing and lower above it.
This pressure difference is the main principle of lift generation.
Wingtip Vortex
The high-pressure air from beneath the wing tends to flow towards the low-pressure area above the wing, this happens along the entire wing, but especially at the wingtips. This is because the wing abruptly ends, in an infinite wing, wingtip vortices would not generate.
This image gives a good overview:

These vortices are a byproduct of the lift generated by the wing and are strongest when the wing generates the most lift, such as during takeoff and landing.
Is all the airflow turning into vortices?

Long story short
The fluid flow dynamics involved in lift generation are complex and subject to many variables. Not all the air will be neatly channeled into the vortices.

While a significant portion of the air contributes to forming these vortices, it's not necessarily true that all of it does. Some airflow may pass around the wingtip without being involved in the vortex creation.
Many variables can alter the actual path of the air; these factors can include:

Dirt or Debris on the Wing: Accumulating dirt, ice, or other debris on the wing can alter the airflow. These contaminants can disrupt the smooth flow of air, potentially affecting lift and drag characteristics. This disruption can also modify the formation and strength of wingtip vortices.

Accessories like Winglets: Winglets, which are vertical extensions at the wingtips, are designed to reduce the strength of wingtip vortices by redirecting the airflow to diminish the intensity of these vortices. They also improve the overall aerodynamic efficiency of the wing.

Wing Design and Shape: Different wing designs, shapes, and sizes will influence how air flows around them, including how vortices form at the wingtips. Factors like aspect ratio, wing sweep, and camber affect aerodynamic performance.

Speed and Angle of Attack: The aircraft's speed and angle of attack significantly influence airflow patterns. At higher angles of attack, which occur during takeoff and landing, wingtip vortices are typically stronger.

hmm okay. My thinking is that the air that the wing is approaching hits the bottom, creating a high pressure there. Then, the air on the upper surface of the wing is becoming lower pressure because the wings surface is blocking the airflow. (To make it easier to understand, imagine the wing at a really high AoA) So after that, the flow leaking from the bottom of the wing would have to all get pulled by the upper surface because the 2 surfaces would have equal and opposite pressure differences. Not to mention the effect of the airfoil curve making the upper surface even lower pressure.

@Wyatt Thinking of airflow hitting the airfoil like bullets striking a plate is a useful intuition only beyond Mach 5 or so.  When subsonic, better than worrying "why does the air do this," just note "it has been observed that the air flows like this near this airfoil under these conditions."  Pulling, leaking, pushing, all eventually lead to fallacies.

@CamilleGoudeseune oh okay, then what would prove my thought process wrong there? Like why is it only useful above Mach 5?

@Wyatt above Mach 5, see https://aviation.stackexchange.com/a/96788/31425 and the other answers there showing how simple things are when hypersonic.  When subsonic, I've found it more useful (not more right, just more useful) to think only of air flowing from high to low pressure, and not going on to call the parts of the flow things like pulling or leaking or whatever.

I will answer from the understanding of question I have,

Firstly, to the question "the air that spills from the high pressure bottom of the wingtip get pulled by the low pressure top of the wing?", I don't think all air that spills form low pressure region reach the top surface since the concept of air as particle can lead it to move it in any path once spilled rather than forming the vortex.

To "Does some air escape past the low pressure top of the wing and not make a vortex at all?" I think yes since there is no mechanism to my understanding that will prevent this.


text:
How does speed and angle of attack affect pressure distribution at the wingtip?
So I was wondering how speed and AoA affect lift distribution at the tip of a wing. For example, if you are flying level and at a high speed, does that mean your wing has more even lift distribution at the tip? (meaning instead of lift decreasing and pressure decreasing as you move toward the tip, it stays more even). Also if you're flying slow and at a high AoA, how does that affect lift distribution?
And how exactly would AoA affect the pressure distribution in those circumstances? (All of this ignoring the effect of tip vortices)
Thanks!

It sounds to me like you aren't firmly separating flight path angle from angle of attack.
The aerodynamics of the wing can be scaled (non-dimensionalized) such that the airspeed does not matter when considering the lift distribution or pressure distribution.
On the other hand, if the aircraft is in level flight (zero flight path angle), then the total Lift is equal to the weight.
So, if you're talking about an airplane (not just an aerodynamic calculation or a wind tunnel model), and you're interested in level flight (L=W), then you  can't consider speed and angle of attack separately.  If you start with a given airspeed, then the aircraft must fly at the angle of attack that provides L=W.
Hopefully you're totally OK with the fact that to slow down, you must increase AoA -- and to fly fast, you must decrease AoA.  The exact values of corresponding AoA to Vtrue will depend on altitude (and weight), but that is why we often work in equivalent airspeed.
So, if I interpret your question as "what happens to lift distribution of a wing as I change angle of attack", then the answer is "it depends"....
In aerodynamics, we sometimes introduce the concepts of the 'basic' lift distribution and the 'additional' lift distribution.  Unfortunately, there are slightly different definitions of these used out there, so while the idea remains the same, the details can differ.
The basic lift distribution is one of:

The lift distribution at zero alpha
The lift distribution at zero lift

The additional lift distribution is one of:

The change in lift distribution for one degree alpha.
The change in lift distribution for a unit change in CL.

1 & 2 will differ in shape and magnitude.
3 & 4 have identical shapes, but one is scaled by the lift curve slope of the wing.
For this discussion, I will use the definitions as 1) and 3).  They are the easiest to work with.
You can think about basic and additional lift distributions as a 3D extension of the idea of superposition in thin airfoil theory (where we decompose an airfoil into a flat plate at angle of attack, a camber line, and a thickness distribution).  This idea falls apart when the wing is stalled.
Using the basic and additional lift distributions, we can write the total lift distribution as a linear combination of the basic and additional (times AoA):
$l(y)=l_b(y)+\alpha\,l_a(y)$
The basic lift distribution depends on the wing planform, twist, and camber distribution.  If the wing has zero twist and zero camber (i.e. the lift is zero for all sections at zero angle of attack), then the basic lift distribution is zero.
The additional lift distribution depends on the wing planform.  It does not depend on the twist and camber distributions.  Recall that variations are sometimes called 'aerodynamic twist', this is because camber can play such a similar role as geometric twist.
So, the answer to your question "What happens to the lift distribution as you change alpha" -- the answer is "It changes by the additional lift distribution" (which only depends on the wing planform).
If you were looking for a simple answer like (it increases at the tips, or it decreases at the tips), then you'll be disappointed because it is more complex than that.  Sometimes it increases, other times it decreases.  It depends.
However, the great news is that it only depends on the wing planform.
So, fire up your favorite VLM type solver (VSPAERO, AVL, XFLR5, etc).  Put in the wing planform you desire, zero camber, zero twist.  Run a single case at one degree angle of attack.  The result is the additional lift distribution for that wing.

Tada!
So, if you know the basic and additional lift distribution for a wing, you can very quickly calculate the overall lift distribution at any angle of attack.
There are lots of cool conclusions that can be derived from these ideas.
For example, if you want to achieve an elliptical lift distribution at a certain angle of attack (or any other targeted lift distribution shape), then for a given wing planform, you achieve the target lift distribution by changing twist and camber.  In fact, if you know the target lift distribution and the additional lift distribution, you can back out the required basic lift distribution.
Or, if you calculate the bending moment of the basic and additional lift distributions, then you can quickly calculate the bending moment of a wing at any angle of attack.
And so on...

ah, okay makes sense thanks for your help. I do have a question : Does the effect where high pressure air on the outside of the wingtip spills to the low pressure zone on the top of the wingtip affect lift distribution? Like as you slow down the air has more time to react, allowing more air to go to the upper surface of the wing (low pressure) affecting the pressure distribution on the top of the wing?

Yes, high pressure air on the bottom interacting with lower pressure air on the top near the tips of a wing are a fundamental part of the lift distribution.  They exist together.  It has nothing to do with slowing down and the air having more time to react.  This behavior is independent of airspeed.  Information travels at the speed of sound in air -- so that sets the speed of reaction.  Incompressible flow is the limit where the Mach number is zero.  In incompressible flow, disturbances are 'felt' everywhere instantly.  Compressibility is generally not important until Mach exceeds 0.6.

oh okay I see. I’m assuming when you’re maneuvering (like pulling back on the stick) that since there’s a higher pressure on the bottom of the wing and a lower pressure on the top (because your wing is making more lift to pull up) the effect I was talking about would be greater, right? (Where the low pressure top of the wing pulls air from the outside high pressure air, affecting the pressure distribution as you pull up)

Yes, but that is not steady level flight (where L=W).  The effect increases because the angle of attack is greater (you are at higher lift coefficient).  When you increase AoA, the overall wing lift distribution will change according to the additional lift distribution.

Ah I see, thanks! (Last question I have) I know that the tip vortices form from high pressure on the bottom of the wing spilling to the top, but is there also an effect where the upper surface of the wing (low pressure) pulls outside air from the wingtip, not from the lower surface of the wing? (Like the upper surface pulls air from directly outwards because of its low pressure)

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
How does more lift help during a stall (ex. flaps deployed)
How does more lift help in a stall? For flaps, I thought the effective increase in camber of the wing would make the wing have a higher AoA, therefore making a stall happen sooner.
Thanks!

Possible duplicate of https://aviation.stackexchange.com/questions/48100/why-does-stall-speed-decrease-when-flaps-are-deployed? Also, by "sooner", do you mean at a lower nose-up fuselage angle in relation to the flight path / relative wind, or do you mean at a higher airspeed? Your question suggests some possible confusion between the two. Just because you change the wing shape in a way that would increase wing's aoa if for some reason the fuselage angle in relation to the flight path stayed constant, doesn't mean that you are increasing the wing a-o-a associated with any given airspd.

@quiet flyer Ah okay, thanks for the link!

In addition of the linked question elements: Flaps (and slats) re-energize the boundary layer, moving the separation bubbles aft, causing the flow to reattach. See this answer for details about the origin of the separation bubbles.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How do tip vortices make downwash?
As seen in this picture, the tip vortices are said to make downwash. Why is that?
I’m also not sure why that’d tilt the lift vector backwards, but that might require a separate question.
Link to the article the picture is from.

There are so many answers here about tip vortices, induced drag, tilted lift and so on, like this one or this one for example...

Your understanding is sophisticated enough that you shouldn't be trying to learn more from websites and other resources intended for pilots and laypersons.  These resources do not apply sufficient rigor -- because rigor is not needed for that audience.
Instead, you should be learning from textbooks intended for engineers.
As you know, a wing can be represented by a horseshoe vortex system with a bound vortex at the quarter-chord line and two trailing vortices from the wingtips.  These all have the same vorticity and can not exist without one another.  Both the bound and trailing vortices contribute to downwash, but I think it is easiest to see how the bound vortex contributes.
I also personally do not like the description of induced drag tipping the lift vector backward -- lift is always perpendicular to the freestream.  The total resultant aerodynamic force might be tipped backward, but not the lift vector.

I see. So the bound vortex is from the boundary layer, I think, and how would that contribute to downwash? I was going off of what this answer said.

@Wyatt:  The bound vortex has nothing to do with viscosity and boundary layers. It is part of potential flow theory.

@PeterKämpf oh right, I completely forgot about that haha

Also, I found this video. Do you think it's accurate?

@Wyatt Despite appearances, I don't have infinite time to spend here.  In particular, I don't have time to watch arbitrary videos and score them for you.  Videos like this one are likely mostly good.  They probably get 95 or 99% of things correct.  However, you tend to ask questions that poke at the last 1% or 0.1% of a subject.  This is good -- as it demonstrates that you're really coming to an understanding.  However, you can't expect a resource aimed at people who only care about the first 80% to meet your needs.

@Wyatt furthermore, the level of understanding that you're seeking is not something that can be achieved through intuition and hand-waving.  To achieve the rigor and subtleness that some of these questions require, you have no choice but to dig into the math and derivations -- something these kinds of resources staunchly avoid.  You're pushing beyond the level that the tools you're using are meant for -- you will be constantly frustrated.  You need to upgrade to the next level of tools.

@Wyatt -- Are you still in school?  If so, what level are you at and how far do you plan on going in your organized education?  If you are done with organized education, how far did you get in organized school and what are your goals?
What country are you in?  If you are not at a university, are you in a city or region that has a technical university?  (I'm asking to judge the availability of technical libraries etc.)

@RobMcDonald I definitely understand not having infinite time. Any help and time that you give me is greatly appreciated. I'm 15, and because of that I haven't gone to any secondary school or anything yet. I really just want to learn as much as I can about this subject, as it's what I'm interested in. I am in the US (Virginia) , and there are some university's in my area.

Also if you would like, we can continue this discussion in chat.


text:
Why is the pressure lowest towards the front of an airfoil?
According to this answer, the low pressure on top of an airfoil is caused by the curving away of the wing (what I interpreted it as). If you look at the lift distribution over an airfoil, you'll see it looks something like the picture below.
My question is, why is the pressure lowest towards the front of the airfoil, when the wing only starts to curve away from the air at the back section? If you look at the waterfall analogy in the link I provided, you'll see what I mean about the "curving away" part.

Thanks! (Also, if there's any answer that answers this question that I didn't see, that's my bad, I seem to have a habit of doing that haha)

This should answers your question.

According to Bernoulli, the pressure drops where the flow speeds up.  The flow hits its highest velocity as it rounds the tight corner around the leading edge -- don't forget to include angle of attack when considering turning.

oh okay, thanks. Do you know if there is an answer explaining why the pressure dops when it speeds up?

Answer: conservation of energy.  https://en.wikipedia.org/wiki/Bernoulli's_principle, and especially https://en.wikipedia.org/wiki/Bernoulli's_principle#Misconceptions

@CamilleGoudeseune oh okay, got it. So basically the air has to have a low pressure zone ahead of it to accelerate, and that will kind of 'stretch' the air out, making it low pressure?

Remember, in every diagram, or explanation, or discussion of this, they are generally not talking about the absolute pressure, or aerodynamic force, they are talking about the pressure relative to the free-stream pressure. I. E., there is really not any suction going on on the top of the wing. The air molecules there are still pushing down on the upper surface. They are just pushing down less than the ones on the bottom are pushing up.

The diagram would be less mis-leading and more accurate if all the arrows pointed at the wing, but were longer, (representing a stronger force), on the bottom. That the artist already uses arrows of different lengths, implying that the length implies the magnitude of the pressure or force, only adds to the mis-representation.

The pressure differential between upper and lower wing surfaces provides lift, and at both the leading and trailing edges of the wing it is zero. Your question is really why does the change in this differential occur more steeply at the front of a wing than at the rear.
The answer is that the structure of front of the wing can abruptly push air out of its path without flow separation while the rear has to use a more gradual curve to keep flow attached to the trailing edge, at least for the upper surface. The thickest section of the wing is usually around the quarter chord and ahead of this a proverse pressure gradient keeps flow attached. Beyond this point an adverse pressure gradient and friction demand more gentle treatment of the flow.
From MIT:

Fluid particles flowing along the top of the wing surface experience a change in pressure, moving from the ambient pressure in front of the wing, to a lower pressure over the surface of the wing, then back up to the ambient pressure behind the wing. The region where fluid must flow from low to high pressure (adverse pressure gradient) is responsible for flow separation. If the pressure gradient is too high, the pressure forces overcome the fluid's inertial forces, and the flow departs from the wing contour. Since the pressure gradient increases with an increasing angle of attack, the angle of attack should not exceed the maximum value to keep the flow following the contour.

The lower surface generally has a proverse pressure gradient on the rear of the wing all the way to the trailing edge and is not critical.


text:
How do I determine the diameter of my propeller at high altitudes?
I'm designing a electrically propulsed HALE UAS and I need to find the diameter of my propeller to find my thrust. Is there an equation for propeller diameter that doesn't rely on knowing my thrust or velocity. In particular an equation that is concerned with relative air density as this is meant to be optimum at high altitude cruise conditions.

You have the process of propeller sizing backwards. This makes the question unanswerable.

I need to find the diameter of my propeller to find my thrust.

Normally, you start with a thrust demand at a given speed and work form there. After all, the propeller is needed to compensate for airframe drag at that speed plus any climb requirements. Without that, you have a glider.
Another route is to start with the torque the engine can supply. Now the propeller has to be able to absorb this torque at the given speed, producing thrust. But you still need to check this thrust against requirements in order to get engine size right.
So please do yourself a favor and find out what thrust you need. The rest should be easy. Use 85% for efficiency to arrive at a suitable $\Delta$v and assume that half of all losses are from friction.
This lets you arrive at $$\frac{\Delta v}{v_{\infty}} = 2\cdot\left(\frac{2}{1+\eta_{Prop}}-1\right)$$ which becomes 16.2% of flight speed for an overall efficiency of 85%.


text:
What Airfix model is this?
I built this Airfix kit when I was younger, and don't know what it is. I'd love to know!

It looks like it could be a Mirage III, but the angle of the photo makes it difficult to be sure.  Do you have any other photographs?

Thanks, I have edited the post with some extra photos that you can look at

I'll stick with Mirage III. There are loads of photos available on Google - take a look and see what you think.

Thank you my friend, I just had a look and found it! I’ve been searching for a good while so though I’d give this a shot, and within a few minutes I found it. Thanks again. Stay safe

Heh. I was going to disagree until I realized the reason the canopy frame is different is because yours is missing the canopy. :)

It is a relatively early Mirage IIIc. You can tell it from other common modifications by the longer rear fuselage, which accommodates the longer afterburner of the older Snecma Atar 9B engine.

The exhaust nozzle on your model is closed indicating military power. On most photos you will see it wide open (it has two buckets on a hinge, and a horizontal gap is clearly visible).
I know all this because not too long ago I built a similar model, but with a smaller 1:100 scale.

Hats off to your model building skills! +1


text:
There is any example/studies/concepts on really short blade jet turbines/turboshafts?
Well, from the little I know, I think the reason jet turbines can't go that fast is because the tip of the blades would reach supersonic speeds and starting to generate too much drag.
However, if, for some reason, the engineer intention is to make a jet turbine/turboshaft to spin really really fast instead of generating thrust (for whatever reason), it would be practical, for example, alongate the length of the turbine and also decreasing the size of its inner blades?
Or if your intention is to just spin really fast, you should just use gear boxes?
I ask that because there could be some applications, like maybe allow for a Ornithopter, perhaps? Just curious.

This ask, or that. Not all ask you. -yoda

Yes there are fast engines around 1 million rpm, not necessarily turbomachines. It turns out this one was built by a spin-off of the University of Zurich. Switzerland is better known for its cuckoos than for its ornithopters though.

The problem is that the engines are as big as they are to get the mass flow rate through them. Smaller engines do spin faster, but they have less power too.

@JanHudec "Smaller engines do spin faster, but they have less power too", for the same quantity of fuel. We can get the same power by increasing air acceleration instead of air mass, but not with the same fuel rate O(N²) vs O(N).

How does spinning really fast relate to ornithopter application?  If you wanted to build a turbomachinery powered ornithoper, existing turboshaft engines (i.e. helicopter engines) should be fine, without changing anything about their spin rate.


text:
How expensive is the structural materials on a stealth aircraft compared to its other components?
Well, I couldn't find much information about the prices on the materials used on stealth aircraft, but nevertheless, its huge price tags are often quite obvious. The B-2 bomber, for example, costs 2 billion dollars.
But of course, these aircraft aren't just its radar signal absorbent composite materials, but its engines, its electronics and so on.
At first, I always thought that the radar signal absorbent materials where the most expensive parts, since no other conventional aircraft used them. But just to be sure, they are as costly as their other components, or they are as cheaper than conventional materials?

These types of costs, as well as the details of the materials themselves, are simply not made public until many years after production, for very good reasons. Plus the technology is not just "radar absorbent" - there are incredible things done with special shapes that reflect radar in a particular way. End result, my understanding (but not an expert, so just a comment) is that very, very few people outside key people in the manufacturers and a relatively small group (much smaller than "all of Congress") of government employees know this stuff. And are sworn to not tell anyone else.

Stealth aircraft are conventional aircraft with airframe shapes and surface coatings designed to minimize radar return and dissipate/mask infrared heat signatures. In some cases flight control systems are different because the designs are aerodynamically unstable and require computerized fly-by-wire to control them in-flight. Their structural materials are not much different than other aircraft though.


text:
Is the same working principle of a vacuum ejector (fluid eductor, pressure ejector or "motive flow") viable to be used as a propulsion system?
Some time ago I've made a question involving Jetoptera bladeless propulsion, and got a comment saying they didn't know how that method of propulsion would make any difference. But I forgot to ask more specifically about said propulsion system.

So, the principle which is normally used in vacuum ejectors or aspirators is normally used to inflate the evacuation slide of an airplane, as fuel injectors, liquid mixers and myriad of other things.

The thing is that the Jetoptera's aircraft claims to use this same motive flow to produce thrust, and like any other company with a "revolutionary idea", it claims it is more efficient at producing thrust than other types of propulsion systems.

More information about how Jetoptera is (supposed to work) in this video and in this video, in the original channel of Jetoptera it only show tunnel testings and gliders with two hollow boxes that you can't even tell if they're actually working.

The question:
Ignoring the claims of efficiency (maybe even the Jetoptera's case itself) and so on: would the motive flow be any good as a propulsion system by itself?

Another duplicate of this question

I'm told that Dyson fans look cool but they actually suck as fans.


text:
Can a Magnus/Coanda effect be used on wings with hot gases for more efficiency? What are current aircrafts that uses such system?
Well, I don't know much about this type of mechanism, and the only post I could find that has something similar to what I'm asking is this one, but isn't quite what I'm asking.
So, the idea would be to expel hot air from holes (or other means) on the surface of the wings in order to increase the lift (or diminish the drag) on wings.
Like what I said, the only airplane that uses such thing is the AN-72, which uses a bit of its exhaust hot gases to increase its lift capabilities. But it is the only aircraft I could find.
I tried to search for "active coanda/magnus effect" and I could only find paid articles, so I can presume this type of technology still is in its early stages?

Coanda effect is well known to indirectly participate in lift creation, for any wing.

Lift is the effect of air pressure on the wing surface. It can only happen if air is maintained in contact with the wing. Coanda effect takes a large role in maintaining this contact and preventing boundary layer detachment. This effect is the tendency for a fluid to follow a surface (note this effect doesn't generate lift by itself). A good illustration of Coanda effect:

Coanda effect, Wikipedia

The airflow around the wing creates lift by Bernoulli principle, this airflow is naturally generated by the displacement of the wing into the air mass, due to the engines.

This airflow can be increased to increase lift. In AN-72, engine exhausts are located over the wing, gas flow is added to air mass flow, this increases lift. This additional high speed airflow is very useful when the aircraft decelerates and the air mass speed also decreases. Exhaust generated airflow maintains a certain level of lift. A similar concept is the channel wing which was studied in the 50s but is not used today.

To create a similar effect, there is no need to expel air from channels in the wing, but a similar idea is implemented: Flaps and slats.

Flaps and slats when extended, which happens mostly at low speed, create additional ways for air to reach the upper side of the wing (top below):

Slat and flaps principle, Source
When aircraft speed has increased, slats and flaps can be retracted (bottom above), because the additional lift they generate comes with a cost in drag.
As regards to expelling air from holes in the wing, this would likely participate to detaching the boundary layer, and would not increase lift. The tendency is to suck up air from holes, to maintain it in contact and prevent it to transition from laminar to turbulent, see What is the purpose of the tiny doors used by the 787's laminar control?


text:
What should be the size of a lifting body aircraft that can carry 5 passengers (385kg/850lbs)?
So I just want to know the size of an aircraft with a lifting body that would fly at low altitudes (around 40 meters/100 feet), and at low speeds (maximum 200 km/h 124 mph). But I don't know if these numbers are even useful to the question.
I tried to search for more aircraft like that, but most of them just fit a single person (the pilot).
I did find some illustrations from reentry lifting body aircraft (like the Martin X-23 Prime), but I can't tell if they are 1:1 or simply an illustration.
I did find the Wainfan Facetmobile FMX-4 quite simple and interesting, I don't know how fast and how high this aircraft can fly, but I think it could be a simple way of scaling things up.
I found this video of the FMX-4 showing its frame and engine (and other stuff), I don't know if it will be useful, but...

Lifting bodies are good for high speed descents like reentry.  I’m no engineer, but even without math I can tell you that you will have difficulty flying 5 adults at 124 mph in a craft shaped like that.  You will need some more wingspan.

"This isn't flying. It's falling with style."

Going slow the problem is lift.  Going fast the problem is drag.  What you have there in the picture is essentially a scaled-up paper airplane design, which works surprisingly well provided there is enough thrust available.
Birds fold their wings back for higher speed flight.  Turboprop carriers also feature undersized straight wings.
What is needed for craft such as these is the ability to take off and land at higher airspeeds.  You won't be landing one of these in the bush or at a small local airport.
Other than that, scaling should be easy.  One might plan for a bit more than 375 kg, considering 5 people, the pilot, and fuel.

which works surprisingly well provided there is enough thrust available. I think it is safe to say that given enough thrust, anything works surprisingly well. ;-)

@DeltaLima - Yes! Just look at the F4 Phantom. :-)  (My absolute favorite airplane as a kid)

NASA extensively studied lifting bodies back in the 60s. Its repository is therefore full with the relevant documents.
I think this, this and this could be useful for your project, but there are really many more.
Anyway I agree with the answer of @qqjkztd: lifting bodies were designed to study the re-entry phase of the future space shuttle and their main purpose was to glide (not fly) at extreme Mach numbers.
Maybe the kind of aircraft you are looking for is a flying wing?


text:
Do boundary layers become thicker or thinner as you speed up?
What happens to the thickness of boundary layers as you speed up? I recently watched a video about the SR-71, in which it said “the inlet spike develops a significant boundary layer of air” when talking about the aircraft at Mach 0.5.
I thought boundary layers got thinner as you sped up, but is it different at such a high speed? The video is here, and it says the things about the BL at around timestamp 4:30.

There are different measures of boundary layer thickness.  The Wikipedia article goes through them.
You'll see that they grow with length along the body, but get smaller with Reynolds number (which increases along the body).  These effects somewhat counteract, preventing linear growth of the boundary layer along the body.  Overall, it does grow along the body.
However, the freestream velocity part is with the Reynolds number in the denominator.  I.e. At higher speed, the boundary layer gets thinner.
Mach 0.5 is slow for an SR-71.
Engines are particularly sensitive to ingesting boundary layer air.  First, ingesting a boundary layer means that the flow entering the engine is non-uniform.  This is more challenging for the turbomachinery -- you can't run as high of pressure ratios because some of the flow will have a different angle than other areas and you will stall the blades.  Consequently, you must back off of what you might have been able to operate at any time you have nonuniform inflow.  Secondly, the air in the boundary layer has had a total pressure loss due to the viscosity.  This means that air will be less efficient in the engine.
Most supersonic aircraft have some sort of boundary layer diverter to avoid ingesting the boundary layer from the forward fuselage into the engine.  Even with that, some also have boundary layer suction in their inlet ramps.

Oh okay, so one follow up question : what exactly makes the Reynolds number increase along a body? The flow would get more turbulent, so does that have something to do with it? Thanks.

You really need to try looking things up before asking here.  Many of your questions would be answered if you would just take ten seconds to google them.  People here want to help, but our time is valuable.  Our time will go a lot farther if you would put in some effort.
The equation for Reynolds number is $Re=\frac{\rho,u,x}{\mu}$.
The $x$ is the distance along the body.  When $x$ increases, $Re$ increases.

I did actually try searching it, but all I got was things about drag coefficients with higher Re numbers. Maybe I’m searching the wrong thing?

It is literally the definition of Reynolds number.  It is a simple equation that should be on every website about Reynolds number.  There are probably a million other things on those websites (including drag coefficients, etc).  But you don't care about those.  Just look at the definition and understand the terms.

I think I was looking at the wrong thing; I found a little more useful information. With higher Re, inertial forces are dominant, making turbulent flow more prevalent. Turbulent flow 'travels' more or mixes between the layers of the BL. Is that what dampens the increase in BL thickness like you mentioned? I appreciate your time!

As you have commented -

Oh okay, so one follow up question: what exactly makes the Reynolds number increase along a body? The flow would get more turbulent, so does that have something to do with it?

The principal controlling factors regarding Reynolds number, are a) velocity of the flow over the surface, and 2) length of the flow path over that surface.  As you may recall, another question that you asked was in regard to turbulence.  But along that line, we must also consider development of the laminar layer and the extent of the laminar boundary layer as the flow progresses over the surface in the downstream direction.  A favorable pressure gradient will enhance the presence of the laminar boundary layer and, remembering that as the object's translational velocity increases, the Reynolds number will increase. Therefore, as a consequence, presence of the laminar boundary layer will be enhanced.  This can occur for the laminar boundary layer up to, and in excess of, a Reynolds number of 60 million! For this to occur, perfection in the surface contour and curvature is paramount.
So what about the turbulent boundary layer?  Several factors come into play because the turbulent boundary layer forms where the flow is progressing against an adverse pressure gradient. Factors regarding the growth and continued attachment of that boundary layer are related to the shape, i.e. concavity, of that surface, and surface condition, i.e. smoothness and curvature, of that surface. In another answer to a question regarding the turbulent boundary layer resulting from surface contamination on the leading edge of an airfoil, the following was noted regarding a comment by FX Wortmann -

Wortmann makes note of a rather startling fact: 'If we compare the roughness height, which will not shift the transition and not increase skin friction, we find for higher Reynolds numbers that the turbulent boundary layer requires usually a smoother surface than the laminar flow…’

Information regarding these aspects of fluid mechanics is readily available in the literature.  Many free resources are readily available on the internet.  Try finding a few of them and take a look. Reading about this will help you understand the different aspects of what is going on.  And if you have the time, a suggestion would be to do the following:  Either in person, or via the internet, take an up-close look at the condition of a modern aircraft and note the perfection presented in its surface construction. A resource for this examination was provided in your last question regarding why boundary layers become more turbulent as they flow over a surface.   A Gulfstream G-800. Note the perfection in the surface smoothness of the wing as evidenced by the reflection of the fuselage, engine nacelle, and tail.


text:
What causes the oscillation in vortex shedding?
When studying this video, I was wondering what actually causes the oscillation? Any source online that I found said that it was from oscillating low pressure zones, but what causes that?

See here for an answer.

@PeterKämpf, Sorry to bother you but do you think the top part of this article is accurate? I just came across it when doing some more research, and it would make sense if it was correct. Thanks

The article looks fine to me.

@PeterKämpf Oh okay, thanks again for your time!


text:
Why doesn't the Coanda effect also pull air from inside the jet / streamline?
As explained nicely in this answer, the Coanda effect will make a streamline of air draw from the surrounding air outside of the streamline. This picture shows it nicely :

So my question is what stops the low pressure created or the 'cavity' from taking said fluid from the inside streamline?

I also can quote the answer I provided :

That fluid that is removed has to be replaced. It sucks in fluid laterally from farther away from the jet

(if that didn't make sense, the answer I linked should clear things up)
Why does it suck in laterally? Why doesn't it also pull fluid from inside the streamline? The force of pressure / a cavity needing to be filled doesn't just act in one direction.
("The streamline" meaning the jet as pictured above)

I get that this isn't directly related to aviation, but one of the topics that is considered on topic for this site is aerodynamics.
(Check here for confirmation.)
As the definition of aerodynamics is this :

the study of the properties of moving air and the interaction between the air and solid bodies moving through it.

I believe that this would be on topic here.

PS IMHO Coanda effect far better explains airfoil lift.

What is the difference between the "cavity" and "inside the streamline"?

@MichaelHall The cavity is where the fluid fills (outside of the streamline from the Coanda effect). The inside of the streamline doesn't experience the Coanda effect, so there is no cavity there.


text:
Does more lift cause a plane to stall at a lower airspeed?
Does more lift cause a wing to stall later? (By more lift I mean a bigger wing) I was looking and saw this question, but the answers didn’t really address why more lift will help a plane not stall.
For flaps I understand, as they reduce the AoA needed to make the same amount of lift. Now that I think of it, is this also true for a bigger wing?
(All of this at the same speed)

I was looking and saw this question, but the answers didn’t really address why more lift will help a plane not stall.

I agree that there's a bit of confusion in the answers to that question that you linked.
When you compare the lifting ability of one wing in different configurations (for example in clean configuration versus with flaps deflected) you have to define in respect to what you make the comparisons. For a wing, the basis for comparison is simply the wing surface in clean configuration: this is the $S$ that normally appears in the equation of any coefficient. If the wing geometry changes (for example due to flaps deflection) $S$ remains exactly the same and any change in the aerodynamic characteristics is condensed in the relevant coefficient. Yes, when the flaps are deployed the wing surface actually increases and therefore the lift as well but the $S$ used in the equation does not change; instead, the $C_L$ increases accordingly: this explains why you normally see a "jump" in the plot of $C_L$ when flaps are deployed:

This approach might sound a bit strange but it is actually the only way to make a fair comparison.

That being cleared up, it's now easy to understand what modifies the stall speed:
$V=\sqrt{\frac{W}{½\rho S C_L}}$
Where $W$ is the weight of the aircraft. If you want to minimise $V$ you can:

decrease the weight $\rightarrow$ toward the end of the flight the stall speed is lower (i.e. safer) than at take off;
increase $\rho \rightarrow$ lower altitudes are safer;
increase $S$ (in clean configuration!) $\rightarrow$ a 15m X 1.5m wing is safer than a 10m X 1m wing (again, both measured in clean configuration);
increase $C_{L_{max}}$ making it make a jump by deploying flaps and slats.

RE:"increase CL increasing AoA", did you mean increase CL-alpha (the slope of CL curve) or simply increase CLmax?

I simply mean increase AoA: $C_l$ is proportional to $\alpha$

I ask because people would assume the AOA is already at α-crit when talking about stall, where CLmax is obtained. So the point is to make CLmax even higher, by deploying high lift devices, regardless of AOA as long as you're at α-crit, as α-crit would possibly change.

There's another aspect I would like to know, if pitching moment coefficient (Cm) should be also considered when calculating stall speed. Is that possible that some statically stable aircraft would not get a positive Cm above certain α that is lower than α-crit, so that it cannot keep nose up even with full elevator deflection, before reaching α-crit?

@LJQCN101: you're right thanks, I'll update my answer. $C_m$ is normally quite constant with $\alpha$ and changes only at stall.

A given level of wing technology (think airfoil choice and all high lift devices) applied to a planform family (same general shape wing, i.e. similar sweep angles and taper ratios and twist approach) will stall at the same $C_{L,max}$.
Since
$C_L=\frac{W}{q\,S_{ref}}$
Then when holding $C_{L,max}$ constant, decreasing wing loading $W/S_{ref}$ will allow you to push stall to lower dynamic pressure (lower airspeed and higher altitudes).

Stall speed
If we decrease airspeed and want to stay level, we need to increase the AoA (actually the lift coefficient $\small C_L$ in the equation below).
As we continue to decrease airspeed, and to increase AoA, we ultimately reach the stall angle. At this point we cannot go slower, and remain level, because to remain level we'd need to have an AoA exceeding the stall angle and we'd stall.
Decreasing the speed while increasing the AoA to remain level is how all pilots are trained to stall and recover from stall. See this video.
Effect of area on lift: Lift is proportional to area
This is what the lift equation says:
$$L = \frac {\rho} {2} V^2 C_L A$$
$\small \rho /2$, which represents air density, can be seen as a constant for this purpose, $\small C_L$ depends on AoA, $\small V$ is the airspeed, $\small A$ is the wing area (and $\small \frac {\rho} {2} V^2$ is what is called the dynamic pressure).
A larger wing deliver more lift. It is also heavier, thus you need proportionally more lift to fly level, but the lift increase is, in some conditions, larger than the weight increase, so it's correct to say a larger wing produces more lift in excess of weight.
Why in some conditions? Because doubling the area doubles the lift produced, but it may more than double the weight, as weight is close to a function of volume. If it were possible to increase lift by increasing the area without limit, then aircraft would be gigantic. It's not the case.
How does area affect the "stall speed"
In our previous situation of decreasing airspeed while increasing AoA, we reached the stall angle at some speed. This speed was the one needed to create the lift required to stay level (so the amount of lift was equal to the weight).
With a larger wing, at the same stall angle and the same airspeed, we create more lift in excess of weight and we climb. We need to slow down to reach the airspeed required to stay level.

Does more lift cause a plane to stall at a lower airspeed?

With our previous definition of the "stall speed", we see with a larger wing, this speed is lower.
Stall occurs at a lower speed, however remember the speed is not the cause of the stall, it's our attempt to stay level by increasing the AoA past the stall angle which stalls the wing, because our airspeed is definitely too slow to stay level.

I see. So I’m a little confused about the last paragraph of your answer. What would make it so a bigger wing would stall at a lower speed? Having more wing surface just increases lift for a given AoA, right?

Ah that edit made it more clear, thanks. So I think another good way to think of it is because for flying level you trim the plane to make a certain amount of lift, large wing or not. This puts less loading per square foot on the wing (for a bigger wing) so it doesn't need to work as hard for the same level of lift, so to speak. Is that accurate?

(tell me if that doesn't make sense haha)

My understanding was that both AoA  AND airspeed were relevant - ie at any specific A0A a stall will occur above, and not below a specific speed?

@MikeB: The critical angle (the stall angle) is the AoA where the slope stops being positive with a load factor of 1g in the $\small C_L$ curve (about 15°). This is where the boundary layer starts detaching from the airfoil. However the "stall speed", as defined in the answer, is influenced by the load factor: The apparent weight depends on total acceleration (gravity + centripetal), thus in a turn the lift required to maintain a level flight is increased, and the "stall speed" is consequently increased.

@Wyatt: Yes, the wing loading (per unit of area) influences the "stall speed", because the larger wing needs a lower airspeed to produce the lift required to maintain a level flight.

I think there's a fundamental problem with this answer.  You say "If we decide it's allowed to descend, then we can continue below this "stall speed" without stalling."  Actually, we have to have a rather extreme descent (or climb) angle before we see much decrease in required lift force, and therefore in stall speed in steady-state flight.  In steady-state flight, required lift = weight * cosine (climb or descent angle).

Now, if you want to say we can greatly lower the stall speed by relaxing the G-loading to significantly less than 1G, that is true, but in general that will cause the flight path to curve more and more downwards, so if we maintain that condition for long, we'll soon be descending quite steeply.  Unless, say, we started the maneuver with the nose pointing quite steeply upwards-- e.g. a 0-G parabolic trajectory to create "weightlessness".

@quietflyer: I wanted to dissociate stall and stall speed, but I'd have used another example. I've removed this confusing (perhaps erroneous) statement.

(PS obviously comments above could be modified to include bank angle.)  Anyway thanks, I think the edit helped improve the answer.

Does more lift cause a wing to stall later? (By more lift I mean a bigger wing)
(All of this at the same speed)

No, stall is related to flow breakdown at specific AOA in a specific configuration (i.e. a flapped configuration has higher amount of lift but slightly lower stalling AOA). At a given speed, more lift than is required to balance the weight will cause a gain in altitude. Think of it as excess power https://www.engineersvault.com/aerospace/a-beginners-guide-to-understand-flight/ since , as you mentioned, "at the same speed," a flapped configuration has both higher lift and drag. Therefore, maintaining the same speed requires pilot action on the throttle.

I was looking and saw this question, but the answers didn’t really address why
more lift will help a plane not stall.

No, more lift will not help with stall, it will only lower the speed required to sustain the flight.
A fowler flap increases both camber and wing area, the effect of the lift is the same as explained above. Yes, an increase in area and camber will have the same effect, increasing the lift.

Well, the mathematics is fairly straightforward.  Because the speed is constant, and assuming the atmosphere is also, the factor $q$ is constant, and we can make the following statement where we will just consider lift (or weight), $W$, and the wing area, $S$, as follows -
$$q\cdot S = \frac{W}{C_L} $$
and rearranging -
$${C_L}\cdot q\cdot S = W .$$
Clearly, now, if we can see that $C_L$ and $S$ are inversely related to one another, with fixed $q$, to give constant lift, $W$. Consequently, if we increase the wing area, the coefficient of lift will decrease proportionately, to maintain the same lift, $W$.  Of course, in this case, we have not considered the modest increase in weight that would occur by increasing the wing area.


text:
How do boundary layers and shocks interact?
How do boundary layers and shocks interact? What difference is made with thinner and thicker BL's? I've recently been researching this topic, but at least for me there are no good search results on google.
(I am aware that this is a very complex subject, and I do not have that much intuition about this subject so far, so take that as you will. Thanks!)

This is not a topic that you are going to find elementary resources to hold your hand.  This is a topic that is studied by graduate and professional engineers.  This is not a topic covered in an undergraduate Aerospace Engineering curriculum.  Consequently, there is no market for plain language textbooks on the subject.  This is an advanced subject and the materials you find are going to be accordingly advanced.
The first results when I google 'shock boundary layer interaction' are all very promising.  If you aren't up to the task of reading a detailed technical paper -- then you aren't up to the task about learning about shock / boundary layer interaction.

Yeah I was aware that this was a complex subject, but I didn't know it was a whole different field of 'fluid studies', so to speak. I think I'll hold off on this subject, as it doesn't really seem to follow my interest in aerodynamics.

This looks more like a comment than an answer


text:
What are the feasibility of making a spherical aircraft using Magnus/Coanda Effect?
Well, I'm quite ignorant in aerodynamics in general, but I couldn't find any aircraft that fits this description. And yes, I know that wouldn't be as efficient as a conventional aircraft, but I'm still curious.
From what I read in this forum about wings and aircraft that uses the Magnus Effect of Coanda Effect on spinning wings aren't as efficient than a fixed wing, and a quote I saw is very clarifying: "a golf ball uses the Magnus/Coanda Effect to fly because it doesn't have wings, an airplane, in other hand, does" (it wasn't in these exactly words, but...).

The idea:

So, the idea is that a magnetic equipment would be inside of a sphere (I can't tell what texture or material such sphere would need) and it would spin the spherical shell so it would use the Magnus/Coanda Effect to change direction and speed. Imagine it like a spinning bullet in the air.
Of course, I can imagine it wouldn't be possible to take off with this thing, even if you somehow made it float (with a magnetic bed, I think).

The problems:

In any case, I can think it would have a lot of problems from taking off and landing. Even so, I'm still curious about how such machine would perform.
For now, I can only think that this thing would hit the ground in a really interesting way.

Your imagination is to be commended, but this question is better suited for worldbuilding SE.  Voting to close as science fiction/fantasy speculation rather than aviation, but I would consider keeping it open if you could make some piece of it actually realistic and/or relevant.  (for example, the spinning spherical shell...)

Search on YouTube and you'll find lots of people who have built models that more or less fly with cylindrical wings using coanda effect.  Overall, it's a pretty safe bet that a serious airplane built like that would suck.  It comes down to what would be the point in the first place.

Not to mention the famous basketball drop down a dam face with a fairly modest spin -- it's got a significant glide ratio by the time it's built up some speed.

There were serious proposals in the 1930s for spherical wing/cabin aircraft with a pivot on the pitch axis and external frame supporting landing gear and stabilizers for control.  I don't recall how they proposed the pilot see to steer...

Three problems that I see with this idea...

Objects like golf balls rotate in flight. The surface facing forward is not the same like it is in an aircraft. The dimples in that case reduce the eddy flows.

From a lift perspective, In static flight it only has reduced drag. It does not generate any lift whatsoever unless it has rotation.

There are better ways to reduce drag that still allow you to generate lift.

It may make sense once we have some form of anti gravity, but then it would just be easier and likely lighter to make something slip streamed and that takes it out of the realm of ASE.

Golf balls most certainly do produce lift -- get a good 3D track of a ball coming off a driver (lowest spin of any club).  Its path is concave upward for more than 1/4 of its flight.  Magnus effect is about lift.  Baseball pitches curve because of Magnus lift.  Set up to spin an empty tube out of a paper towel roll and you can make it do a loop.

Both only because they are rotating. Aircraft cannot rotate in that manner and still fly.

Go look at an archive of Popular Science and Popular Mechanics magazine covers from, say, 1925 to 1940.  You'll see at least three or or four ways this was seriously proposed (though I don't know that any of those aircraft were actually built).  Hint: helicopters pass control to the rotor from the non-rotating fuselage, either through a hollow main shaft or via swash plate (fixed on one side, spinning on the other).  Yes, you need external engines and stabilizers with 1930s tech, and providing vision for an interior pilot was probably an unsolved problem in the day...

Helicopters do not rotate the body around the propulsion. It is a fixed structure. You would have to carve gouges in the body to pass the mast and tail and that would create so much drag as to negate any benefit from Magnus/Coanda.

I don't know why the neg, you might disagree with me and that is fine. but I also don't see you giving an answer either.

I downvoted because your answer is wrong.  A spinning sphere does produce lift, drag reduction by the dimples on golf ball is unrelated.  Reducing drag with those dimples clearly does not preclude lift production.

@ZeissIkon I fixed that point in the answer when you pointed it out. it should read clearer now. and I'm not debating a spinning sphere. I'm talking about an aircraft that holds people or cargo and participates in flight operations. This is the Aviation stack, not the physics stack.

From the question: "and it would spin the spherical shell".


text:
Could small ramjets on the tip of propellers allow for supersonic spin of turbine blades?
Well, of course, if it was practical, someone would've already done that, but I'm still curious.
As you can imagine, I'm an illiterate on the matter of aerodynamics, and even though supersonic propeller blade driven aircraft is not feasible because of the tremendous forces they would suffer, I see it as a somewhat of a "barrier". "What would be possible if this weren't a problem?", so to speak.
Well, I can imagine that putting a ramjet at the tip of a propeller would increase complexity and increase the size of said propeller (so all components could fit in), which would increase the drag, but could allow for more air to be pushed.
The closest thing I could find was "Tip Jet", a type of helicopter that uses combustion at the tip of the blades. One of the various attempts had ramjets at the tips, the "Doblhoff WNF 342", but there isn't much information, and I'm more curious about the applications on turbines (which would be tremendously complex).

This question seems very similar; does it help?

It seems that you mean "turbine" as a generic word for the jet engine. Technically turbine is something opposite to a propeller (spins when blown onto rather than blow when spins). Are you talking about propellers/fans, i.e. propulsion?

@Zeus a little of both. If you can make a propeller move this fast, why not a fan?

Supersonic propellers make a lot of noise.  So much that airplanes fitted with supersonic propellers were injuring the crew.  And even people on the ground as they would takeoff, land, or just fly overhead.  Look up the "Thunderscreech" as an example.

The turbine is usually rotating the propeller, not the contrary. If this is the propeller which drives the turbine, then there is no need for a turbine. "I'm an illiterate on the matter of aerodynamics", that's not a matter of aerodynamics, it seems you missed the principles of engines in the first place.

Spinning fast is not a problem. In fact, for a turbine-driven engine, it's easier: turbine is an inherently fast-spinning device. So much so that tips of the compressor fans are typically supersonic: slowing them down would require a heavy gearbox and/or a large multi-stage turbine. (Though both solutions are used to some extent).
There is no particular problem with "tremendous forces" (that could be helped by tip thrust) either. The centrifugal forces on the vanes/blades greatly exceed aerodynamic forces (which cause torque and could be negated by the tip jets). Witness foldable propellers you can see on many drones and airplane models: the blades usually don't have any lock and are held in place purely by centrifugal forces. On jet engines, the vanes often rattle when not spinning: they also have some freedom of movement. So, the blade must withstand "tremendous force" anyway, and more so if it's supersonic.
The problem is just the aerodynamic efficiency. Supersonic airflow is significantly less efficient to harness useful force from it, thus designers do everything to avoid it, instead of doing tricks to achieve it as you suggest. Still, as I mentioned, for turbines it may be difficult, and they might allow it.
The tip jets are only useful for helicopters. And there, they are not used to achieve higher speed, but rather to eliminate torque on the shaft, which reduces or eliminates the need for the tail rotor.

Usually, compressor blades are fully subsonic. It is only the fan where blade tips reach supersonic speed.


text:
Are there any aircrafts that use the same "ballooning effect" of spiders to fly?
For those that aren't aware, the "ballooning" effect that spiders use to glide (not necessarily fly) explaining in a simple way, some small invertebrates throw a bunch of long strings (in the case of spiders, spider silk) in the wind, and because of a mix of static electricity and hot air streams, it allows them to take off.
Of course, this method normally works for just a few meters, but if the spider is lucky enough to catch a wind stream, they can glide for miles.
Anyway, is there any aircraft that uses a similar method to fly?
Assuming that ion propelled aircrafts that uses ionisation of air aren't considered ballooning effect aircrafts.

Do balloons count?

@MichaelHall if they use static electricity to float, then yes.

No.
Phenomena that we observe of objects in the miniature realm do not scale up to our size. Small insects are capable of many things that humans are not, as in this example:  Water Strider
Asking if you could build a plane that mimics the behavior of an infant spider would be like asking why you cannot walk on water.
(... or noting the dome-like shape of a small bead of water on your car, and asking if you could take your garden hose and spray up a pile of water to form a swimming pool without sides.)
There simply isn't enough energy in static electricity to levitate something with any significant weight.


text:
References for lift and drag coeficient formula/values
I'm looking for references for values/formula for lift and drag coenficients. In this paper https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6244461 it is said that

$C_L(α)$ and $C_D(α)$ are the lift and drag coefficients

I recall seen a formula with $\cos(\alpha)$ and $\sin(\alpha)$ but I'm not been able to find again. Since I have to run some simulations to this dynamics it would be nice to have some formula for these coefficients if someone could give me a direction.

If you give us more information about your simulations we can for sure give a better answer

Hi, so, I want to run a optimal control simulation to do some test (let say the controls to make minimize the descent from two points. For this I would need the dynamical equations, which are already present on the reference, and the coefficients of drag, lift and wing surface area.

Select an aircraft of interest; we do not know what aircraft that is.  There are excellent answers such as by quiet flyer, here or this question by Robt DiGiovanni here. Methods are usually presented as an abstract from which aspects of interest may be determined. Maybe this will help.

Acctually have to check the method and I thought it would be a nice model to test it on. So I don´t have any particular aircraft in mind, just one that I could find the data availabe to

Not wanting to make your task even harder, but the full equation is a Taylor series.

I'm looking for references for values/formula for lift and drag coefficients

The USAF STABILITY AND CONTROL DATCOM is freely available and contains plenty of coefficients.
In particular, chapter 4.1.3. contains methods to evaluate the $C_L$ of the whole wing (chapter 4.2.1 evaluates the contribution to $C_L$ due to the body/fuselage but this contribution can be disregarded as a first approximation). "Method 1" at page 503 of the PDF should give you the needed value based on the actual planform of your wing.
Conversely, chapters 4.1.5 and 4.2.3 evaluate $C_D$ of wing and body respectively.
For the wing you have two terms, one independent of the lift and one dependent on it. The first term can be evaluated with the method starting at page 722 while the latter with the method starting at page 758.
Also for the body/fuselage you have two terms that you'll find at page 939 and 1008 respectively.
Do not be scared by the page count! You won't find any complicated equations in the DATCOM, only simple empirical/statistical equations mainly based on graphs. At the end of each method you'll also find an example that you can reuse simply changing the parameters with the ones of your airplane.

Check out Flight Mechanics Theory of Flight Paths by Miele chapter 6 diagrams show $C_D$ vs. $C_L$. $C_L$ is proportional to $\alpha$ (wing alone the slope is about $\frac 1{2\pi}$ per radian. (Hint: view at archive dot org.)


text:
What scale is the speed trend line on a PFD's ASI?
A primary flight display (PFD) in a glass cockpit has an airspeed indicator (ASI) that doesn't just display the speed, but also a vertical arrow or bar that shows the "speed trend" i.e. the acceleration. But there's no extra "acceleration scale" shown behind it like there is for speed. What's the scale of this trend arrow and how do you read it?

Direct answer from the A320 FCOM:

Speed Trend (yellow)
  This pointer starts at the speed symbol. The tip indicates the speed the aircraft will reach in
  10 s, if its acceleration remains constant. The pointer only appears, when it is greater than 2 kt,
  and disappears when it is less than 1 kt.
  It also disappears, if the FACs fail.

It is also a good indicator during change of attitude. To understand what your aircraft is doing. Because you will see a change in the trend before seeing a change in the vs indicator which allow you to react to a deceleration or acceleration.
I have more data from OEM for the functionnality, unfortunately they are protected. I cannot diffuse more of that explanation.

I found some training material on Airbus PFDs which explains:

A vertical arrow, called the speed trend arrow, indicates the aircraft's
  predicted speed in 10 seconds if the current acceleration or deceleration rate remains constant.

Put another way, if you measure the acceleration in knots per second, and then multiply it by ten, it's on the same scale as the speed tape.
If you want to reach a particular speed in ten seconds' time, adjust pitch or power to put the head of the arrow on that tick on the speed tape, then keep adjusting to keep it on the same tick as it approaches.

then keep adjusting to keep it on the same tick as it approaches. Then it will forever take another 10 seconds to get to that speed, i.e. you never get there.

@DeltaLima: But it will lead to the target speed being approached exponentially, which is pretty good as control principles go, even though it doesn't exactly achieve "reach a particular speed in ten seconds' time".

Yeah, that's a good point. I was just trying to write another way of interpreting it, but as you say, it's not quite right.

On the Garmin G5, used in many small airplanes, (under 12,500 lbs), the air speed trend is interprated thusly:
The Airspeed Indicator displays airspeed on a rolling number gauge using a moving tape. The numeric labels and major tick marks on the moving tape are marked at intervals of 10 knots. Speed indication starts at 30 knots, with 60 knots of airspeed viewable at any time. The actual airspeed is displayed inside the black pointer. The pointer remains black until reaching never-exceed speed (VNE), at which point it turns red.
A color-coded (red, white, green, yellow, and red/white “barber pole”) speed range strip is located on the moving tape. The colors denote flaps operating range, normal operating range, caution range, and never-exceed speed (VNE). A red range is also present for low speed awareness.
The Airspeed Trend Vector is a vertical, magenta line, extending up or down on the airspeed scale, shown to the right of the color-coded speed range strip. The end of the trend vector corresponds to the predicted airspeed in 6 seconds if the current rate  of acceleration is maintained. If the trend vector crosses VNE, the text of the actual airspeed readout changes to yellow. The trend vector is absent if the speed remains constant or if any data needed to calculate airspeed is not available due to a system failure.
See the Pilots Guide, Para. 2.1.1, page 14.
https://support.garmin.com/support/manuals/manuals.htm?partNo=K10-00280-00&language=en&country=US
Here's a picture of the G5
https://static.garmincdn.com/en/products/K10-00280-00/v/cf-lg.jpg

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do TFRs create a de facto Class C airspace around untowered fields?
Inspired by this question:
If a TFR requires discrete squawk and two-way ATC (Class C requirements) whenever within the airspace, and an untowered field exists within the TFR's boundary, does that untowered field essentially become a quasi-towered field?
If I'm to remain in two-way comms with ATC (presumably Approach), it will be difficult to coordinate with other traffic on CTAF.  On the other hand, they all need to be on the same frequency to be in two-way with ATC.  If we're all chatting away to coordinate on our own, that would seem to jam the frequency pretty badly... does Approach take over sequencing us? What's the procedure for landing at that field under these conditions (Obviously departures will need to be released by ATC.)?
I assume patternwork basically gets shut down? If not... do we get option clearances from Approach? (That seems... not ideal since they don't have eyes on the runway...)

TL;DR: No. Class C airspace comes with a specific set of requirements for pilots and a specific set of requirements for ATC. TFRs have "squawk and talk" requirements for pilots, but that does not mean ATC has Class C requirements.

With all TFRs, it is imperative to read the actual text of the TFR itself and not make assumptions based on what similar TFRs may have required in the past. Let's examine this VIP (POTUS) TFR, which is FDC NOTAM 4/4691. Generally POTUS TFRs will always be the same, but just keep that in mind.
The overarching restriction is "No pilots may operate an aircraft in the areas covered by this NOTAM (except as described)." We knew that, but it's important to read this anyway; some TFRs only apply to certain types of aircraft. It makes you sound unprepared when you request permission to fly your Skyhawk into a "No UAS" TFR.
Then they list exceptions to, and more details about, the blanket restriction. Note that it is possible for ATC to authorize other exceptions "in consultation with the Air Traffic Security Coordinator via the Domestic Events Network." In your linked question the controller probably did not do this coordination and so it was probably an error on their part. But in theory ATC can authorize any deviation from the blanket restriction. In theory.
Paragraph A is for the "inner core" of the TFR and basically says you aren't flying your private Skyhawk into or out of there, no way no how.
Paragraph B is for the "outer ring" of the TFR and now things become relevant. Among other restrictions (no loitering, etc) it says:

ACFT MUST BE SQUAWKING THE DISCRETE CODE PRIOR TO DEP AND AT ALL TIMES WHILE IN THE TFR AND MUST REMAIN IN TWO-WAY RADIO COM WITH ATC.

This means exactly what it says: You must be on ATC's frequency as long as you're physically able to be (line-of-sight to ATC's radio antenna). If you feel that you need to be on CTAF, then in my mind you have two options: Make sure your aircraft has two operating radios, so you can transmit and listen on CTAF while still monitoring ATC... or wait for the TFR to end. I'm not a lawyer but that's how I would interpret it. Remember though that CTAF calls aren't mandatory—just highly highly encouraged.
In contrast, for Class C there is more to the airspace than just "squawk and talk." (In fact the "squawk" requirement is also different between TFRs and Class C airspace. The TFR requires a discrete code, while Class C only requires an "operable transponder" responding on the ATC-specified code, which may be the non-discrete 1200 code.)
Within Class C airspace ATC will separate IFR-to-VFR traffic, and this service is not part of the TFR. Within Class C airspace ATC will sequence VFR traffic to the primary airport, and this service is also not part of the TFR; note that even in actual Charlie airspace you can have non-towered satellite airports within the surface area, and ATC will not sequence to those non-towered airports.
For a TFR, you will contact ATC on the ground to get your discrete squawk code and your release from the airport. As always, ATC will never issue any runway clearances (takeoff, landing, option) for a non-towered airport.

As for pattern work: Again, read the TFR. Paragraph C lists the many types of operations which are specifically not authorized within the TFR:

FLT TRAINING, PRACTICE INSTRUMENT APCH, AEROBATIC FLT, GLIDER OPS, PARACHUTE OPS, ULTRALIGHT, HANG GLIDING, BALLOON OPS, AGRICULTURE/CROP DUSTING, ANIMAL POPULATION CTL FLT OPS, BANNER TOWING OPS, SIGHTSEEING OPS, MAINTENANCE TEST FLIGHTS, MODEL ACFT OPS, MODEL ROCKETRY, UNMANNED ACFT SYSTEMS (UAS), AND UTILITY AND PIPELINE SURVEY OPS.

To play devil's advocate, a very pedantic argument might be that non-"training" pattern work—a licensed pilot going up for currency, say—would still be authorized. Good luck making that argument, given the spirit of the rest of the prohibitions.

I think you may be overthinking things by using terms of art like "de facto Class C" and "quasi-towered field."  Really you just need to be talking and squawking.  That's generally all the TFR will specify.

does Approach take over sequencing us?

They should provide whatever sequencing services they normally do depending on airspace and the flight rules in effect.

What's the procedure for landing at that field under these conditions?

Expect a normal full stop landing.
Personally I have only flow in and out of TFRs at a towered field where approach did hand us off to tower.  However, as you noted in the other question the standard practice when landing at a non-towered airfield is for an approach controller to have you squawk 1200 and pass you to CTAF.
As answers to the other question indicated, that flight should have remained on an ATC frequency and kept their squawk until landing, so that would be the procedure to expect.  Therefore, if the controller absentmindedly spouted the standard "squawk VFR, change to advisory approved" it would be prudent to reply "will remain with you until clear of the TFR / landing."
If you are concerned with not making normal CTAF calls, remember there shouldn't be anyone in the pattern, and everyone inbound or outbound should be talking to ATC.  At some point it may be prudent to ask, and in non-standard situations just use plain language.  For example: "approach, N123W, is there any arriving or departing traffic between me and the field?"

Obviously departures will need to be released by ATC...

Yes, departures will need to be released by ATC.

I assume patternwork basically gets shut down? If not... do we get option clearances from Approach?

That would be a good assumption.  Since the "R" in TFR is intended to ground anyone not flying into or out of the TFR on a flight plan, it wouldn't make sense for pattern training to continue as if there were no TFR.  And it would make less sense for a radar controller to play tower for the reason you mentioned.


text:
Where is the GA community at regarding fuel/engine types?
I promised myself that I would pursue my PPL if I successfully completed my phd. I'm now doing research about the when/how I should do this, and one of the big factors for me is that there's no point in getting a license if I can't afford to fly on the regular.  Purchase price is obviously a factor here, but so are fuel costs - and as a climate/energy policy scholar I can't look at fuel without wondering about the future of avgas.
From this perspective, turboprops seem to be in a nice, futureproof spot since biodiesel and synthetic fuels will likely keep anything that can run on diesel-derivatives going regardless of fossil fuels' fortunes.  Aside from ethanol, though, gasoline doesn't have any decent alternatives that I'm aware of.  But boy howdy do turboprops seem heinously expensive - and basically require one to buy way more aircraft than I think I'll ever have need of (though my long-run dream is to trick out an OV-10 as a bush plane).
Am I overthinking the whole thing here? Is there any anxiety about the future of fuels and what it could mean for piston craft?  How does a potential new owner go about selecting for things like powerplant/fuel based on their expected use cases?

Is your question "How does a potential new owner go about selecting for things like powerplant/fuel based on their expected use cases?" If so it's quite difficult to answer. What are your expected use cases, and your initial and yearly budget?

How long do you expect to continue flying your first airplane?  The way I read it, gasoline will be available for surface vehicles (and hence for light aircraft) for at least another fifteen to twenty years, even if we actually manage to stop selling new fossil fuel cars and trucks in ten years or so.

@mins I'm looking for a sort of procedural overview, rather than to solve for my specific circumstances, as my own specs are likely to change, but my expected use cases are medium-run passenger + (a lot of) luggage, with the occasional (no more than annual) New England<->Nevada trip.  Budget is part of what I'm solving for.

@ZeissIkon My understanding is that mogas in piston aircraft is technically doable, but not very safe, so I'm not sure I see the link between the duration of automotive gasoline use and the production of avgas? But I expect I have ~30 years of life as a pilot in me, and won't be planning to go through planes like I would autos in that time; and I drive all my cars until they're totaled.

Forget CO2, the huge problem is avgas is the last remaining fuel that contains tetraethyl lead, ongoing replacement efforts have failed to yield a substitute, and the EPA is under pressure to outright ban it. (Plus there's one company that's left making it, and one major lawsuit or plant explosion may very well end supply.)

My understanding is that many of the newer (i.e. post 1990?) light plane engines -- including classic models made in that time frame -- are rated for mogas, as long as the octane requirement is met.  Back when cars were converting, "all" it took was changing valve seat material -- something that could be included in a routine engine overhaul.  Meeting 100 octane without ethanol or lead is harder than protecting engine parts that depend on lead.

@ZeissIkon Not comparable. If you've been following the FAA PAFI, there were multiple concerns about material compatibility, longevity, power, etc. that simply are not (as much) as a safety concern for an automotive environment. You're talking about engines that refuse to use fuel injection and electronic igntion due to safety. For example, when ultra-low sulfur diesel came in, it is well known and documented that it causes fuel system leaks and injector wear. That's not acceptable to the FAA.

I bet my bottom dollar there will be a viable ecological synthetic substitute for gasoline within the next 15 years. Combustion engines are too good of a concept to trash alltogether.

“there's one company that's left making it” Wow, that's all I needed to hear.  No wonder you can't get avgas at random airports around the world.

@Harper-ReinstateMonica Not only is TEL itself hard to come by, and probably facing an EPA ban as soon as the FAA certifies an alternative, there’s only one refinery left willing to work with it. Every batch they make requires a complete cleaning of the entire refinery, and lead can’t be transported in pipelines either. It’s expensive for a reason.

Never lose sight of the fact that the primary purpose of all US Federal safety organizations (including the EPA and the FAA) is not-very-covert protectionism for US industry. Major industry players get to write whatever regulations they like. If you don't accept that inconvenient truth, explain why in recent memory, two aircraft types from a US manufacturer were only grounded by the FAA after the rest of the world had already grounded them.

Gasoline (-like fuels) may come from power-to-fuel when electricity is cheap enough. The charm (and curse!) of synthetic hydrocarbons is that the entire gasoline and Diesel infrastructure (fuel transportation, storage, distribution, combustion engine based vehicles) can stay in continued use.

@alephzero Not everything that annoys you is a conspiracy. Lead in fuels is actually bad, mmkay?

@user253751 - lead in fuel isn’t a bad thing, AVGAS manufacturers don’t put it there as a prank.  However, lead in the environment, particularly (pardon the pun) when ejected into the atmosphere in atomic-scale dust, most certainly is a bad thing.

"as a climate scholar, I want to burn GHG-emitting fuel in large quantities for recreation" what?

@Frog where do you think it goes after the fuel is used up?

There are alternatives to 100LL. All require STC's. One is Mogas, but a new 100LL replacement has just received FAA certification as a 100 octane unleaded gas that can be used alone or mixed with any percentage of 100LL. GAMI received certification for their 100UL fuel, and they will soon be issuing STC's for all the engines used on Cessna 172's. Additional aircraft and engines can simply be added to the approved list. Pricing, however, will be slightly higher than 100LL, and the STC pricing hasn't been established yet but the company thinks $200 for the 172's is about right.

From the perspective of someone who knows more about energy technology than about aviation:  Look at paragliders, hang gliders, or maybe winch-launched gliders.  Or buy yourself a fancy simulator.

First off there are piston engines certified for flight and built by Continental that burn Jet-A which I suspect will be in production for the rest of our lifetimes as it powers most of the air fleet out there (i.e. jets and turbo props). Classic designs like the Piper Archer are being built with these engines now which has helped move this into the mainstream by making a super common airframe available with an alternative fuel source. Diamond also makes some higher performance piston aircraft that run on Jet-A like the DA-42 so there are alternatives out there that allow light aircraft to not be reliant on gasoline.
There is also a big difference that sets this whole situation apart from the car gasoline/battery/alternate fuel debate. The FAA; ultimately for something to fly in this country (and I assume you are talking about the US) it must be in some way certified by the FAA (or flown under the experimental category). As such the FAA has largely only approved 100LL and 110LL for use in aviation engines, or better the engines are only certified for use with those fuels. There are some engines that have MoGas conversion options but a big chunk of the fleet ultimately runs on 100LL which creates an interesting supply/demand situation. It's well within the interest of the refineries to continue to make 100LL since there is a very clear market for it, there are no threats of alternatives because there are no certified alternatives. Considering how hard FAA certificates are to come by it would be hard to come up with a new, flight certified, technology fast these days.
Pilots also tend to stick with what they know, and we all know the smell of 100LL...
Makers have been looking for an alternative to 100LL since car fuel stoped using led years ago, and has only managed to certify a single engine to use a new non led fuel as recently as a few weeks ago.
So, sure, one day in the future there may be no more 100LL, there may even be no gasoline, there might be no jet fuel, or even no liquid fuels of any type but that day is likely far off in aviation. Electric aircraft are still a relatively young reality in the useable/production vehicle space and battery energy density is still a real issue to make it competitive.
It ultimately takes two to tango and the FAA (and other governing bodies) will need to certify a non gasoline/Jet-A based power plant that is installed on or STC'ed into a common airframe produced in sufficient numbers to offset the current aviation fleet. On account of the fact that the aircraft that I fly still has ash trays and a working ADF (not that there are any NDB approaches left around me); Im not really worried about things changing too fast...
You can find some of the FAA's updates on the matter here.
Also related

If your really worried, dont buy a plane, join a club

Thank you so much for the club link. That possibility had completely escaped my notice.  Accept this answer because of the wealth of useful links for me to continue on with.

@WilliamWalkerIII Ive been a member of two clubs at this point (changed due to a move) and rented from various flight schools. Both have been great experiences with great planes that are easy to access and delightful to fly. Dollar for dollar is a way easier path to flying than ownership and I have generally found the planes to be available and well kept.

are they generally available for longer duration trips. e.g. if I decided to get a chunk of hours in the air by hauling some burner friends to Reno, staying there myself (for ease of access to card rooms more than anything else) and then flying them home some days later be doable under a club?

@WilliamWalkerIII it depends on the club and their rules (each one will have different policies) but generally the planes are available for multi day trips. My club allows multi day trips but I can only have one booked at a time.

@WilliamWalkerIII Generally, clubs have a minimum number of billed hours per day for overnight trips, but the exact rules will vary for each club.

Diesels are also most efficient, and similarly tolerant of fuel variations to turbines, so they are likely to accept any future alternate fuel if one is approved for turbines. Makes them all around good choice for a new airplane.

Matter of time before somebody, maybe California, puts their foot down and says "no more leaded avgas. Done."

My vague understanding is that hydrogen's a more likely replacement than electric-powered planes, but also still a pretty long way off if ever.

@llama for that extra little bit of glide range when your tanks are (practically) empty!

"ultimately for something to fly in this country (and I assume you are talking about the US) it must be in some way certified by the FAA (or flown under the experimental category)" Is there really anything stopping the OP from building a biodiesel-powered plane and registering it as an experimental aircraft? They've got a PhD, after all; would there be any usage restrictions on it or anything?

@nick012000 nothing aside from complexity; a fair number of kits/experimental planes are based on known designs, parts, engines and other hard to make things with custom airframes/wings/slippery-ness improvements. Slapping any ol' engine in a plane is not always as easy as it looks no matter the level of education.

@nick012000 Late to the party, but also: my PhD is in public policy (energy policy in particular). I am not to be trusted with engineering challenges of any kind, let alone aerospace engineering. XD

Unless you are independently wealthy, you’re going to be flying a piston plane, which means either gasoline (of some sort) or diesel.
There are a few diesel piston engines, which are normally run on jet fuel (aka kerosene), but they’re somewhat rare, and rare means expensive both to buy and to maintain. This is disappointing since these would seem to be the clear path forward, but it’s a classic chicken-and-egg problem.
However, 99% of light aircraft use some sort of gasoline.
Leaded avgas is by far the most common, and also by far the most harmful to the environment. The good news is that most engines under 200hp run just fine on ethanol-free mogas; all you need in most cases is an STC and some placards to make it legal. The key is these engines never needed 100LL (or its predecessor 100/130) in the first place; they ran just fine on 80/87 or maybe 91/96.
Note that finding ethanol-free mogas can be somewhat challenging, but it is far cheaper than leaded avgas. And while the very long term future of mogas isn’t great, it’ll be around for the foreseeable future.
For avgas engines over 200hp, which do typically need 100LL, several companies have been working with the FAA on substitute high-octane unleaded fuels, and there may finally be a light at the end of that tunnel. But as a niche fuel it’ll be expensive, especially if the under-200hp folks all switch to cheap mogas instead. Long term, it would be cheaper to just replace all those engines with diesels.

Re "they ran just fine on 80/87", not always the case.  A number of engines required the intermediate grade that used to be produced, with octane rating in the low 90s IIRC).  So my Cherokee 180 (Lycoming O-360 engine) has an autogas STC (and runs fine on it), but it has to be premium, not regular.

@jamesqf Added reference to 91/96; I assume that’s what you meant.

Actually, this issue cannot be overthought.  The plane that is purchased will have to be lived with or, if not, sold to get something else.  Other than the usual host of questions about the mechanical condition of the candidate plane for purchase, and the cost of power-plant/propeller overhaul and inspection certification, will be the cost to bring the plane to FAA compliance.  All of this seems to be set on the cost of operation as an ultimate deciding factor.  The question always seems to come down to the following; can the plane of choice be bought, maintained, certified, and flown at a reasonable cost.
Within a broad perspective, the overall most important issue in purchasing a plane generally seems to involve the cost of operation.  The dilemma that was mentioned should be viewed from the perspective of G100UL aviation fuel, details of which can be viewed here. In July of 2021 the FAA approved Supplemental Type Certificates (STCs) authorizing use of G100UL high-octane unleaded avgas in aircraft piston engines, without modification.  At least this is something to consider, in the foreseeable future piston-engine aircraft are not likely to be rendered unserviceable due to the unavailability of leaded avgas, or the need to modify engines to use unleaded G100UL fuel.
Given this view, a perspective of the future of piston aircraft would be that they will not be likely rendered obsolete within a relatively short period of time, but, if they are FAA compliant, will retain their value and remain viable for a rather considerable time.  There are no other alternative energy packages that have a similar or greater energy content per unit mass as does avgas in the operation of current-technology piston engines. Consequently, the purchase of a piston powered aircraft will likely remain viable for the intended period of use, at the end of which time the plane will be sold.
Also, keep in mind that retrofitting an aircraft of current design for a new type of power plant, say battery-electric, will be a "big hairy deal" should the power-to-mass ratio of batteries become viable for the required longer operational range of flight that will be demanded of such aircraft.   Certifying a piston aircraft for such a conversion is not likely to be easy, or even considered rational, particularly regarding the safety issues, rebalancing, and wing-loading issues that must be overcome to keep the aircraft stable and flyable.  In view of this issue alone, piston-powered aircraft in their current state of design and use are likely to be around a very long time, especially when unleaded avgas is available. Or at least, that is the way things seem at the present time.

"This issue cannot be overthought." Sweeter words, to an academic's ears, do not exist.

One more take on the subject: for the safety of you and others, I suggest you start your flying hobby with the most cost efficient (read: cheapest safe) setup, and fly, fly & fly. Every dollar you save on the equipment and invest in flight hours, is like money in the bank.
You can seriously start thinking about the deeper concerns of this issue when you have hundreds of hours of flight time. No need to worry about availlability of different fuels and the market scene before that.

This has been part of my calculus, but thank you for making it explicit.

The wonderful world of aviation is full of temptations, it is very easy to drift from the essentials. God knows I've done it...

Yes, you're overthinking the whole thing. I won't repeat what others have said about diesel and mogas (but I agree).
The airplane you buy now is not necessarily the airplane you'll be flying 5 or 10 years from now. The bottom line - now - is that you're pretty much stuck with 100LL (or if you you make an effort, mogas).
Things will change. But not quickly. Eventually we'll get practical electric GA airplanes, once the batteries get good enough. It'll be years before we see that in experimentals, and more years before the FAA gives its blessing for certified aircraft.
For now, just buy what you can afford (buy less - you'll have money leftover for the unexpected, which you should expect) and go fly.
When things change, you can always sell and buy something else.

There are electric GA airplanes certified by the FAA (e.g. Pipistrel Alpha) since 2018. They are probably not very practical for longer flights yet, but it's not a certification issue, just battery capacity.

Yeah, I think it's a blunder to think you'll keep airplanes for a long time.  Especially if one drives cars til they're totaled.  Most Youtubers who are pilots have gone through a series of airplanes.  I also think it's a huge mistake to leap straight into a highly technical airplane like a turboprop, there have been high profile accidents where the novice pilot was overwhelmed by workload.


text:
How do Pistons vs. Turbines fare during a Carrington event?
Electromagnetic pulses are a staple in sci-fi, and they're basically the writers' hand-waving of "deletes technology" weapons.  This question asks about whether or not GA motors would survive such a thing, and the answer seems to be "a big enough EMP will still cook it, but it'll take more to kill the mags than it would the GPS and radio."  A far more likely scenario of concern, however, is solar storms.
The Carrington Event was a titanic Coronal Mass Ejection(CME) that damaged telegraph networks, ionized the atmosphere powerfully enough to produce dramatic aurorae, and is viewed as a possible global catastrophe scenario given the broad dependence on large electrical power grids.  The event carried on long enough that a 7-line conversation took place between Boston and Portland after both stations had disconnected their power supplies.
Unlike an EMP, which delivers one powerful shock to the system, solar storms produce prolonged periods of induced current in exposed hardware.
Obviously radios and sensitive electronics are hosed, and possible permanently lost. But what are the likely effects on aircraft engines?
Carrington events are legitimate considerations for electrical system planners and disaster management professionals, but I'm wondering if they're of concern for the aviation sector?
For a specific case, The Long Dark's story begins with a De Havilland Beaver becoming uncontrollable due to a Carrington Event (while being operated in hilariously questionable weather, to boot).  The DHC-2 comes in radial and turboprop versions, however, so I'm curious if one or the other of these propulsion schema would be preferable to someone concerned about solar storms?

Related article: Impact of Space Weather on Aviation

I don't know what would make it "uncontrollable" since the flight controls are operated by cable circuits, like a clothes line you hang your washing on, more or less.
It would come down to what the effect would be on the 1920s vintage electrical parts in the engine magnetos, like coils, points, capacitors etc. So if the event could effect those sorts of components, say inducing fields in the windings of the magneto coil, the engine might quit or might start to misfire so badly it achieves the same result. If electrical transformers are affected by these things, then it's possible a magneto would be as well.
If it was a Turbo Beaver, its PT6-20 turboprop had a hydromechanical fuel controller, so the engine would keep running once started, even if the electronics and electrical instrumentation were fried, because the fuel control is based on mechanical inputs and mechanical air pressure sensing devices.
So if I had to chose which one would be most likely to be impervious to an electromagnetic event, it would be the Turboprop version. Even with newer 80s vintage TP engines that are electronically trimmed, if the electronics goes out it just rolls back to a mechanical fuel schedule that runs less efficiently.
On the other hand, a FADEC turboprop, one of the more recent ones from the 90s on where fuel control is completely electronics dependent, would probably have a problem however.